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Avalanche Forecast

Archived

Feb 20th, 2021–Feb 21st, 2021

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Kananaskis.

Strong winds are making the upper snowpack more reactive as windslabs develop in most open areas. A storm with strong winds is forecast to reach the region on Monday. 

Confidence

Moderate -

Weather Forecast

Sunday will see the warm front with the associated precipitation begin to move into the region. There will only be minor accumulation on Sunday before the main mass of the storm arrives on Monday with 15-20cm of snow. Winds are still going to be strong out of the SW so as the storm begins to arrive we can expect avalanche danger to increase. 

Avalanche Summary

No new natural avalanche activity was observed on Saturday but conditions felt primed for human triggered avalanches due to the presence of these new windslabs. 

Snowpack Summary

The effects of the recent winds are noticeable with windslabs in open terrain at treeline and above. These windslabs are 10-20cm thick in areas travelled on Saturday but we can expect them to increase in depth and reactivity as winds continue overnight. Any windslab that starts in the upper snowpack will likely step down to the Jan 29th persistent interface down 40-60cm. Watch for these problems along ridgelines, and in lee terrain mainly on N and E aspects. 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Pay attention to isolated alpine features as well as cross-loaded features at treeline.
  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Watch for areas of hard wind slab on alpine features.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.